Inductive electrical component



United States Patent Ofifice 3,183,466 Patented May 11, 1965 3,183,466INDUCTIVE ELECTRICAL COMPONENT Joseph J. Marius, New Providence, N.J.,assignor to Nytronics, Inc., Berkeley Heights, N.J., a corporation ofNew Jersey Filed May 27, 1963, Ser. No. 283,225 6 Claims. (Cl. 336-192)This inventioin relates to improvements in electrical components andmore particularly to improvements in the electrical characteristics ofsuch components.

In the manufacture of certain radio frequency inductors it is verydesirable to employ leads which are made partly of ferromagneticmaterial, such as for example dumet leads, because of their good weldingcharacteristics. However, the presence of such a ferrous metal withinthe electrical field of the inductor results in a substantial amount ofelectrical degradation of the coil. This degradation is measurable interms of the Q, that is the figure of merit of the coil and its effecthas been found for certain values of inductance to decrease the Q of thecoil by an amount up to approximately 35%. This prob lem becomes moreacute for inductors of miniature and subminiature size since in theseinductors the degradation cannot be significantly reduced by relocationof the leads.

Accordingly it is an object of this invention to provide an electricalinductor in which the electrical degradation of the coil due to theeffect of the leads is either entirely eliminated or at leastconsiderably minimized.

It is another object of this invention to provide inductors of miniatureor subminiature size having substantially higher values of Q than couldbe obtained heretofore in inductors of equivalent size which employedferromagnetic leads.

All of the objects, features and advantages of this invention and themanner of attaining them will become more apparent and the inventionitself will be best understood by reference to the following descriptionof an embodiment of the invention taken in conjunction with theaccompanying drawing, in which:

FIG. 1 shows in axial cross section one embodiment of an inductormanufactured in accordance with the principles of the invention,

FIGS. 2a and 2b show enlarged views of the type of lead employed in theconstruction of FIG. 1, and

FIG. 3 is a graph showing a comparison between the Q values of coils ofprior art construction and those made according to this invention.

Referring now to FIG. 1, a coil is wound about a coil form or core 12which in the drawing is cylindrical in shape, but which may be othershapes as Well. Fhe core 12 is preferably of ferrite but may also bemade of iron, phenolic or other suitable material and is provided withan axial bore 14, which as shown, may extend from one end of the core tothe other. Leads 16a and 16b are inserted in the bore 14 at oppositeends of the core 12. If desired the bore may be replaced with a recessat each end of the core. The ends 18a and 18b of the coil 10 aresuitably connected as by soldering or welding to the leads 16a and 1612.

Referring now to FIG. 2, each lead 16a, 16b comprises a nib portion 20and an elongated portion 22. The nib portion 20 is made of a suitablenon-ferromagnetic material such as for example copper, and is buttWelded to the elongated portion 22, forming an enlarged section or knot24 at the junction of these two portions. The portion 22 may be a dumetwire or other wire either partly or entirely made of ferromagneticmaterial. The nib portion 20 is preferably provided with serrationsproduced by mechanically deforming, as at 26, so that the nib 29 will befirmly anchored in the bore 14. The knot 24 limits. the travel of theleads 16a, 16b into the bore 14 so that the ferromagnetic portions 22 ofthe leads is prevented from entering the body of the coil form.Consequently/the ferromagnetic portion 22 are maintained for the mostpart in the region outside the effective range of electromagneticinfluence or field of the coil, resulting in an immeasurable orsubstantially reduced effect on the Q of the coil depending upon theinductance value thereof. The limited insertion feature afforded by theknot 24 also serves to produce uniformity from unit to unit duringproduction, resulting of course in more uniform Q values for a givennumber ofunits. sembly of FIG. 1 is then encapsulated within a suitablematerial 28 such as epoxy resin to protect it from the deleteriouseffects of the atmosphere.

FIG. 3 shows a graph which illustrates the advantages of the improvedconstruction of the invent-ion. In this graph the abscissa represents ona log scale the inductance values of various coils or inductors and theordinate represents their Q values. The curve A illustrates the drop inthe Q values of inductors of various values as a r sult of priorconstruction which employ a ferromagnetic lead in which a portion of thelead was projected into the field or range of infiuence'of the inductor.From this curve it will be seen that the decrease in the Q value of thecoil is very substantial. Curve B illustrates the Q values for a numberof inductors made with the improved lead construction of the invention,from which it will be observed that for inductors having certain valuesthere is no measurable electrical degradation, i.e. decrease in the Qvalue of the coil.

Thus the lead construction and arrangement described above provides asubstantial improvement in the electrical characteristics of theinductors so manufactured. Specifically I have found that approximatelyof the inductors made according to this invention having inductancevalues between 0.1 microhenry and 180,000 microhenries have exhibited nomeasurable decrease in the Q of the coil when the nib portion 20 is madeof a non-ferromagnetic substance, such as copper. This is particularlyimportant in miniature inductors where size is at a premium and thedesigner cannot therefore aiford to increase the length of the assemblyin order to prevent degradation by positioning the leads substantiallyoutside the range of influence of the coil. For some of the coils madewith prior constructions the decrease in the Q of the coil was found tobe as high as approximately 26%, see FIG. 3; the Q values of such coilswas found to decrease only approximately one-half of this figure whenusing the construction according to this invention.

While the foregoing description sets forth the principles of theinvention in connection with specific apparatus, it is to be understoodthat the description is made only by way of example and not as alimitation of the scope of the invention as set forth in the objectsthereof and in the accompanying claims.

What is claimed is:

1. An electrical inductor assembly comprising, a core, a coil of wirewound about said core, an electrical conductor connected to one end ofsaid coil, and another electrical conductor connected to the other endof said coil, said conductors each including a first portion ofnon-ferromagnetic material and a second portion of ferromagneticmaterial, each of said first portions extending within the eiiectiverange of electromagnetic influence of said coil, and substantially allof said second portions being disposed outside the effective range ofelectromagnetic influence of said coil.

2. The invention described in claim 1 wherein said core includes arecess at each end thereof, said first portions of said conductors beingheld in said recesses.

3. The invention described in claim 2 wherein said conductors eachinclude an enlarged section at the junc- The as tion of said first andsecond portions, and said first portions of said leads being held bymeans of a snug fit in said recesses with said enlarged sectionsadjacent the ends of said core.

4. The invention described in claim 1 wherein said first portions ofsaid conductors comprise copper and said econd portions of saidconductors comprise durnet lead wires.

5. The invention described in claim 1, which further includes a mass ofresinous material completely encapsulating said assembly to therebyisolate said assembly from the deleterious substances of the atmosphere.

6. An electrical inductor assembly comprising a coil of wire, a core offerromagnetic material positioned within said coil, said core having anaxial bore therein, a lead wire connected to one end of said coil, andanother lend wvire connected to the other end of said coil, each of saidlead wires having a first non-ferromagnetic por- References Cited by theExaminer UNITED STATES PATENTS 1/51 Kohring M 336-205 X 2/58 Hopkins etal 336-192 X OTHER REFERENCES Electronic Fundamentals and Applications(Ryder), published by Prentice-Hall (New York), 1953 (page 15 288 reliedupon).

JOHN F. BURNS, Primary Examiner.

1. AN ELECTRICAL INDUCTOR ASSEMBLY COMPRISING, A CORE, A COIL OF WIREWOUND ABOUT SAID CORE, AN ELECTRICAL CONDUCTOR CONNECTED TO ONE END OFSAID COIL, AND ANOTHER ELECTRICAL CONDUCTOR CONNECTED TO THE OTHER ENDOF SAID COIL, SAID CONDUCTORS EACH INCLUDING A FIRST PORTION OFNON-FERROMAGNETIC MATERIAL AND A SECOND PORTION OF FERROMAGNETICMATERIAL, EACH OF SAID FIRST PORTIONS EXTENDING WITHIN THE EFFECTIVERANGE OF ELECTROMAGNETIC INFLUENCE OF SAID COIL, AND SUBSTANTIALLY ALLOF SAID SECOND PORTIONS BEING DISPOSED OUTSIDE THE EFFECTIVE RANGE OFELECTROMAGNETIC INFLUENCE OF SAID COIL.